On Tue, 23 Jan 2018, Fabrice Gasnier wrote:

On 01/23/2018 02:32 PM, Lee Jones wrote:

quoted

On Tue, 16 Jan 2018, Fabrice Gasnier wrote:

quoted

STM32 Timers can support up to 7 dma requests:
4 channels, update, compare and trigger.
Optionally request part, or all dmas from stm32-timers MFD core.
Also, keep reference of device's bus address to allow child drivers to
transfer data from/to device by using dma.

Signed-off-by: Fabrice Gasnier <redacted>
---
 drivers/mfd/stm32-timers.c       | 37 ++++++++++++++++++++++++++++++++++++-
 include/linux/mfd/stm32-timers.h | 14 ++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c
index a6675a4..372b51e 100644
--- a/drivers/mfd/stm32-timers.c
+++ b/drivers/mfd/stm32-timers.c

@@ -29,6 +29,23 @@ static void stm32_timers_get_arr_size(struct stm32_timers *ddata)
 	regmap_write(ddata->regmap, TIM_ARR, 0x0);
 }
 
+static void stm32_timers_dma_probe(struct device *dev,
+				   struct stm32_timers *ddata)
+{
+	int i;
+	char name[4];
+
+	for (i = STM32_TIMERS_DMA_CH1; i <= STM32_TIMERS_DMA_CH4; i++) {
+		snprintf(name, ARRAY_SIZE(name), "ch%1d", i + 1);
+		ddata->dmas[i] = dma_request_slave_channel(dev, name);

And if any of them fail?

Hi Lee,

If some of these fails, reference will be NULL. It is checked in child
driver (pwm for instance) at runtime. Support is being added as an
option: pwm capture will simply be unavailable in this case (fail with
error).

Can you place a simple one-line comment in here please.  Or else
someone will come along and add error handling for you.

quoted

quoted

+	}
+	ddata->dmas[STM32_TIMERS_DMA_UP] = dma_request_slave_channel(dev, "up");
+	ddata->dmas[STM32_TIMERS_DMA_TRIG] =
+		dma_request_slave_channel(dev, "trig");
+	ddata->dmas[STM32_TIMERS_DMA_COM] =
+		dma_request_slave_channel(dev, "com");

Can you format these in the same why.  This hurts my eyes.

I use enum values and try to match as possible with reference manual for
"up", "trig" & "com" names.
Would have some suggestion to beautify this?

I just mean, can you push the first  dma_request_slave_channel() call
on to the next line, so each of the calls are formatted in the same
manner please?

quoted

quoted

+}
+
 static int stm32_timers_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;

@@ -44,6 +61,7 @@ static int stm32_timers_probe(struct platform_device *pdev)
 	mmio = devm_ioremap_resource(dev, res);
 	if (IS_ERR(mmio))
 		return PTR_ERR(mmio);
+	ddata->phys_base = res->start;

What do you use this for?

This is used in in child driver (pwm) for capture data transfer by dma.

Might be worth being clear about that.

Perhaps pass in 'dma_base' (phys_base + offset) instead?

-- 
Lee Jones
Linaro Services Technical Lead
Linaro.org ? Open source software for ARM SoCs
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